FIG. 1 (Prior Art) is a simplified perspective view diagram of a typical wall switch motion sensor 1 contained within an electrical wall box 2. Wall box 2 is in turn embedded in a wall 3 of a building. The electronics of the wall switch motion sensor 1 include a switch that can be closed such that AC current is made to flow from AC Live line 4, through light 6 (for example, an incandescent light bulb), and to AC Neutral line 5, thereby causing light 6 to emit light. The electronics of the wall switch motion sensor 1 can also open the switch such that no current flows through light 6, thereby turning off the light.
Wall switch motion sensor 1 includes a multi-section lens 8 (for example, a multi-section Fresnel lens). The motion sensing circuit detects movement of an infrared-emitting object (for example, a person) that moves in front of the lens. In response to this detecting, the motion sensing circuit either turns on light 6 or leaves light 6 turned on. If the motion sensing circuit detects no movement of an infrared-emitting object in front of the lens 8 for an amount of time, then wall switch motion sensor 1 may, in one case, cause the switch to decouple AC Live line 4 from AC Neutral line 5, thereby turning light 6 off. The wall switch motion sensor 1 thus conserves electrical energy by reducing energy usage when no person is detected to be occupying the room. Conversely, if a person is occupying the room and moves in front of lens 8, then wall switch motion sensor 1 closes the switch, thereby turning light 6 on, or keeping light 6 on. A user may also manually turn light 6 on or off using a manual power switch 7.
FIG. 2 (Prior Art) is an exploded view of the wall switch motion sensor 1 of FIG. 1, showing how the wall switch motion sensor is disposed within the electrical wall box 2 in the wall 3. Wall switch motion sensor 1 is customarily attached to electrical wall box 2 using a pair of screws 9 and 10. A face-plate 11 is customarily situated to cover the edges of the wall switch motion sensor 1 as illustrated. The face-plate is also customarily attached via screws 12 and 13.
FIG. 3 (Prior Art) is a simplified top-down cross-sectional view of multi-section lens 8 (a Fresnel lens) within the wall switch motion sensor 1 of FIGS. 1 and 2. The view shows how lens 8 works to allow a wall switch motion sensor 1 to detect motion. Lens 8 includes several sections. Each section directs infrared radiation from a corresponding respective one of several zones onto a pyroelectric infrared detector 12. Detector 12 is sometimes referred to as a PIR detector or a PIR sensor. The term PIR detector will be used here.
When there is a source of infrared radiation in a zone of the field of view of a section of the lens, infrared radiation received from the zone is directed by the section onto detector 12. When a person emitting infrared radiation passes across the field of view of lens (moving downward in the illustration of FIG. 3), infrared radiation emitted in a first zone 13 is first directed by a first section of lens 8 onto detector 12. Then, as the person moves further and enters an area 14 which is between zones, the intensity of infrared radiation as detected by detector 12 decreases because the source of infrared radiation is no longer in the first zone 13. There is no section of lens 8 that directs onto detector 12 the infrared radiation emitted in the area 14 between zones. As the person moves farther across the field of view (farther down in the illustration of FIG. 3), the source of infrared radiation enters the second zone 15 in view of lens 8. The section of lens 8 associated with this second zone 15 therefore directs more infrared radiation onto detector 12. The resulting increasing and decreasing of infrared energy that is incident on detector 12 is interpreted as a person moving from zone to zone in the field of view of the motion sensor.
FIG. 4 (Prior Art) is another diagram that illustrates movement of a person 16 across the field of view 17 of lens 8. As person 16 moves from the left to the right and into a first zone 18, a section of lens 8 focuses the incident infrared radiation onto detector 12, thereby causing detector 12 to detect an increase in infrared radiation intensity. As person 16 continues moving to the right, person 16 exits the first zone 18 and enters an area 19 between zones. Lens 8, however, directs less infrared radiation emitted from this area 19 onto detector 12. Detector 12 therefore detects a decrease in infrared intensity. Finally, person 16 moves into a second zone 20. A section of lens 8 focuses infrared radiation from zone 20 onto detector 12. The electronics of the wall switch motion sensor 1 interprets the increase and decrease and increase in a signal output by detector 12 as being due to a person moving in the field of view of the wall switch motion sensor.
In a particular wall switch motion sensor, the actual operation of the optics and the PIR detector may be somewhat different than in the simplified, single-element detector described above. The description above is set forth for background information purposes. As is known in the art, there are dual-element detectors and quad-element detectors that operate in slightly different ways. In each case, however, a mechanism for selectively directing infrared radiation from zones in the field of view onto a PIR detector.
In addition to wall switch motion sensors, there are other wall box circuits for controlling lights such as remote controlled wall switch dimmer systems. FIG. 5 (Prior Art) is a simplified diagram of one such system. The system involves a wall switch dimmer circuit 21 situated within a wall box 22, and an infrared remote control 23. The infrared remote control 23 is of a type typically used to control electronic consumer devices (for example, televisions, DVD players, stereo systems). Remote control 23 communicates infrared (IR) control signals encoded onto a specific carrier signal. These IR control signals are received by a corresponding infrared receiver 24 situated in wall switch dimmer 21. The infrared receiver 24 is a narrowband receiver that is tuned to the frequency of the carrier signal. The receiver in the wall switch dimmer can therefore detect the IR control signals as transmitted from infrared remote control device 23 in the presence of noise such as background incident infrared radiation. Other infrared signals that are not properly encoded onto the carrier are, however, rejected and ignored by the infrared receiver 24.
A user of remote control device 23 can turn light 6 on or off manually by pressing on a paddle switch 25 on the wall switch dimmer 21. Manual dimming and brightening may be performed by pressing on a dimmer rocker switch 26. By pressing up or down on the dimmer rocker switch 26, the user may manually cause the intensity of light to gradually increase or to gradually decrease. Indicator lights 27 indicate the degree to which the light has been dimmed.
The same on/off and dimmer functions can be controlled by pressing appropriate keys/switches on remote control 23. Paddle switch 28 can be used to turn on and off light 6. Rocker switch 29 can be used to change the brightness of light 6. Wall switch dimmer 21 responds to IR control signals from remote control device 23 by changing the duty cycle on-time of a switch such that the average amount of energy supplied to light 6 via AC Live line 4 and AC Neutral line 5 is controlled, as is known in the art. Unfortunately, the remote controlled wall switch dimmer system of FIG. 5 involves a narrowband infrared receiver that only receives and properly interprets particular IR control signals carried on a particular carrier frequency. If the special remote control 23 is lost, then the user can no longer control the wall switch dimmer 21 remotely. Moreover, using the special remote control device 23 involves yet another remote control device in the typical house, which may clutter the user's environment.
FIG. 6 (Prior Art) is a simplified diagram of a prior art infrared receiver circuit 30 that on first inspection might appear to offer a solution to the problem of having to have a specialized remote control device to control dimmer 21. Infrared receiver circuit 30 is a narrowband receiver that self-tunes to detect IR control signals carried on numerous possible different carrier frequencies. Infrared receiver circuit 30 includes several LC tank circuits, each of which is tuned to the frequency of a particular carrier signal to be received. A digital logic circuit 31 switches between these tank circuits by opening and closing switches 32, 33 and 34 until one of the tank circuits begins to resonate in response to an incoming IR control signal. Unfortunately, providing the infrared receiver circuit 30 and its numerous tank circuits in a cost-sensitive wall switch dimmer would likely be prohibitively expensive. Moreover, if specialized remote control 23 is to be dispensed with, then another remote control that the user has would be made to operate with dimmer 21. Due to the great variety of different types of remote control devices present in the market place, programming the receiver circuit of the circuit of FIG. 6 to detect and respond to control signals from any selected one of these numerous different remote controls in a given user application would be cumbersome. Employing the circuit of FIG. 6 therefore does not provide an economically viable way to dispense with the specialized remote control of FIG. 5 in a light dimming application. It is expensive and cumbersome. An alternative way of controlling lighting is sought.